Compensation control system for cathode-ray recording tube



Dec. 2, 1969 A Y BAKER, JR., ET AL 3,482,255

COMPENSATION CONTROL SYSTEM FOR CATHODE-RAY RECORDING TUBE Filed Dec. 6,1967.

5 Sheets-Sheet l De.2,19e9 M. BAKER, J'R, Em. 3,482,255

COMPENSATION CONTROL SYSTEM FOR CATHODE-RAY RECORDING TUBE Filed nec. 6.19e? 5 Sheets-Sheet 2 Dec. 2. 1969 A. Y. BAKER, JR., ET AL 3,482,255

COMPENSATION CONTROL SYSTEM FOR CATHODE'RAY RECORDING TUBE Filed Dec. 6.1967 5 Sheets-Sheet 5 Dec. 2, 1969 A. Y. BAKER, JR., ETAL COMPENSATIONCONTROL SYSTEM FORy OATHODE-RAY RECORDING TUBE Filed Dec. 6. 1967 5Sheets-Sheet 4 @L www N v .Ewhww W .n NEW m.. N QN EN@ N NNN ENW E ENTR.m EN Eq Q NN A A s. .NIMM NWMW QN* NN\\AM WNWMNM-WV QQ* H1 IN .mv m EN-REQNRNEQ Nag.

' De@ 2, 1969 A. Y. BAKER, JR., ET AL 3,482,255

COMPENSATION CONTROL SYSTEM FOR cATHoDE-RAY RECORDING TUBE Filed Dec. 6,1967 5 Sheets--Sheexl 5 United States Patent O 3,482,255 COMPENSATIONCONTROL SYSTEM FOR CATHODE-RAY RECORDING TUBE Arthur Y. Baker, Jr.,Encino, Calif., and Lonnie K. Lindsay, Tulsa, Okla., assignors toCentury Geophysical Corporation, Tulsa, Okla., a corporation of OklahomaFiled Dec. 6, 1967, Ser. No. 688,413 Int. Cl. G01d 9/42 U.S. Cl. 346-1104 Claims ABSTRACT F THE DISCLOSURE An improved cathode-ray display andrecording instrument is described which is capable of responding toelectrical input signals to display and record numeric or othercharacters represented thereby; and which incorporates a compensationcontrol system for permitting high speed operation of the instrumentwithout over-printing of successive lines, or other reproductiondefects.

BACKGROUND OF THE INVENTION United States Patent 3,289,196-Hulldiscloses a cathode-ray type of display and recording system andinstrument in which an electron beam in a cathode-ray tube iS caused torespond to applied electrical signals to trace out numeric or othercharacters on the display screen of the tube.

The mechanical details of the aforesaid instrument are described indetail in United States Patent 3,121,604- Hull. As'described in thelatter patent, a light-sensitive paper is drawn across the face of thecathode-ray display tube to be exposed to the characters displayedthereon. A permanent record of the displayed characters is, thereby,provided on the sensitized paper. The characters themselves aresequentially displayed in a line across the face of the cathode-raytube, and the sensitized paper is moved in a transverse direction withrespect to the line, so that each subsequent line of charactersdisplayed on the cathode-ray tube appears in a displaced position withrespect to the preceding line on the paper.

A limiting factor in the speed at which the displayed characters can berecorded on the sensitized paper in the aforesaid system and instrumentis the time required t0 move the sensitized paper from one line to thenext. For example, it is' possible in the system sequentially togenerate a line of characters across the face of the cathode-ray tube ina few microseconds. However, it requires a few thousand microseconds todraw the sensitized paper from one line to the next.

In an attempt to speed up the operation in the prior art systems, andprior to the advent of the present invention, it has been the practiceto record each line of characters while the paper was in motion. Thisresults, however, in a skewing of the successive lines of information onthe sensitized paper; and it also results in a tendency to `overprintthe rst two lines of information, each time the paper is moved. Forcontinuous printing, the overprinting problem occurs only on the rst fewlines. However, when the printing is not continuous, the overprintingwill occur throughout the text. The line skew, which is undesirable froma comprehension standpoint, occurs at all times.

The compensating system of the present invention is constructed tocorrect the skew eifects, so that even though the paper may be in motionwhen a portion of a line of information is printed, the information atall times is recorded in a straight line extending across the paperwithout skew and Without any tendency to overprint other lines.

The line compensation control system of the invention "ice across thepaper in a straight line, without skew, may be realized.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a simplified block diagramof a display and recording system in which the line compensation controlsystem of the present invention may be incorporated;

FIGURE 2 is a plan view of an instrument embodying the compensationsystem and apparatus of the present invention in one of its embodiments;

FIGURE 3 is a schematic perspective representation, partly in blockform, of the control system of the invention;

FIGURE 4 is a circuit diagram of a photocell amplier which may beincluded in the system of FIGURE 3;

FIGURE 5 is a logic block diagram of a four-bit counter which may beincluded in the system of FIG- URE 3; and

FIGURE 6 is a circuit diagram of a digital-analog converter which alsomay be included in the control system of FIGURE 3.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT The system shown in FIGURE 1is similar to the display and recording system disclosed in the Patent3,289,- 196 referred to above. The simplified block diagram of FIGURE lincludes a source 10 of binary coded data. This source, as explained inthe said patent, may be a counter positioned in a receiving station of atelemetering system, it may be an electronic digital computer, or it maybe any other appropriate source of binary coded data.

The source 10 introduced the binary coded data to a blanking signalgenerator 12. This generator, as also explained in the said patent,transforms the coded input signals into appropriate blanking signals.The blanking signals from the generator 12 are applied to a blankingcircuit 14. The blanking circuit 14 is connected to the input electrodeof a cathode-ray tube 18. The cathode-ray tube may include the usualbeam-forming electrodes and deection plates. An electron beam is formedin the tube, and the electron beam is blanked at proper intervals byblanking signals applied to the input electrodes by the blanking circuit14.

The electron beam in the tube 18 is deflected horizontally andvertically across the face of the tube. A liber optic system 22 ismounted on the face of the tube 18. As the electron beam of thecathode-ray tube 18 is deilected across the screen of the tube, theresulting light produced by the screen is projected by the opticalsystem 22 onto a light sensitive paper 26, as the paper is drawn acrossthe face of the tube. It will be appreciated that the tube 18 iscontrolled so that a sequence of characters is inscribed on its screenin a line extending across the screen, which line is recorded on thepaper 26. The process is then repeated, and another sequence ofcharacters is formed in a line across the screen of the tube 18. Thesensitized paper is moved so that each line of characters is recordedunit 28, A clock input from a suitable clock source 27 is applied to thelogic unit 28. A printcommand is also applied to the unit 28, and thedisplay and recording of each separate character by the tube 18 andsensitized paper 26 is initiated upon the receipt of the print commandfrom, for example, the computer or other source of binary coded data.

As each character is displayed by the system of FIG- URE l, an end ofcharacter command is formed, and the latter command is returned to thesource of binary coded datato indicate that the system is ready for thenext character.

The clocking unit 28 is coupled to a deflection signal forming generator30 which applies synchronizing signals `to the blanking generator 12, asdescribed in the Patent 3,289,196. The generator 30 also forms theappropriate deflection signals which are amplified in a line, orhorizontal deflection amplifier 32, and in ,a field or verticaldeflection amplifier 33. The horizontal deflection signal amplifier 32and vertical deflection signal amplifier 33 apply appropriate deflectionsignals respectively to the line (or horizontal), and to the field (orvertical) deflection plates of the cathode-ray tube 18.

As fully described in the Patent 3,289,196, the system of FIGURE lcontrols the cathode-ray tube 18 so that the series of charactersappears in a line across the screen of the reproducing tube 18. Asmentioned previously herein, each such line of information normally willskew, whenever the paper is in motion as the beam is scanned in the linedirection. As also pointed out previously, this skewing effect in someinstances also has tendency to cause one line to be printed over apreceding line on the paper as the paper is moved.

The line compensation control of the present invention senses the motionof the paper across the face of the cathode-ray tube 18, and produces ananalog signal which is used to compensate for the aforesaid skewingeffect.

In the plan view of FIGURE 2, the cathode-ray tube 18,\for example, isshown supported on one side of a housing 100, the housing serving toencase the various components which go to make up the display andrecording instrument. In the instrument of FIGURE 2, the sensitizedpaper 26 is drawn from a reel (not shown) by a roller 102 around a guideroller 103 and across the face of the cathode-ray tube 18. The actualdrive of the paper, and the other mechanical components of theinstrument, may be equivalent to those shown and described in the Patent3,121,604.

`In the instrument of FIGURE 2, the drive roller 102 is driven by amotor 104 whose shaft is directly coupled to the roller 102. The drivemotor 104 may, for example, be a stepping type of motor. For example, ina constructed embodiment the motor stepped in each activation through anarc of and served during the stepping motion to move the paper 26 yfromone line to the next across the face of the cathode-ray tube 18. Thatis, ideally between the printing on the paper 26 of each line ofinformation displayed on the face of the cathode-ray tube, the motor 104is actuated, so as to step through an angular distance of 15, to presentthe next line of the paper to the screen of the cathode-ray tube.However, as explained, in order to speed up the recording by theinstrument, the recording of each line on the paper is started beforethe paper has actually been moved to the next line and while it is stillin motion.

In carrying out the concepts of the invention, an optical disc 106 isattached to the shaft of the drive motor 104, on the side of the drivemotor opposite to the drive roller 102. A light source 108 is providedin a bracket 110, and light from the light source is focused by a lens112 on the optical disc 106. A photocell 113 is mounted in tite6 bracket110 on the opposite side of the optical disc By constructing the opticaldisc in accordance with known techniques, so as to have one opaque markand one translucent mark for every degree of the disc, when the motortakes a single step of, for example, 15 as mentioned above, fifteenincrements are generated by the optical disc, so that the photocell 113generates fifteen pulses. It will be appreciated, therefore, that forevery step the motor takes, fifteen pulses are generated by thephotocell 113. The repetition frequency of the fifteen pulses, and thetime interval during which the burst of fifteen pulses is generated,depends upon the speed at which the motor turns during its particularstep.

As clearly shown in FIGURE 6, the pulses generated by the photocell 113are amplified in a solid state photo amplifier 200, which will bedescribed in detail subsequently in conjunction with lFIGURE 4. Theamplified pulses from the photocell amplifier are fed to a four-bitbinary counter 202, which will be described in conjunction with FIGURE5. The complemented outputs from the counter 202 are fed to a simpleresistive type of digital analog converter 204 which will be describedin conjunction with FIGURE 6. The output of the converter is applied tothe vertical deection plates of the cathode-ray tube 18 as acompensating voltage.

As mentioned above, in a particular constructed embodiment, the steppermotor 104 takes a 15 step for each line of advance of the sensitizedpaper 26. The resulting fteen pulses derived from the photocellamplifier 200 are fed to the four-bit binary counter 202, which is resetto zero each time the stepper motor is energized to advance the paper26. Then, as the motor rotates through each of its 15 steps, the countercounts the pulses produced at the output of the photocell amplifier 200.When the motor completes its particular step, the counter will normallyhave counted to fifteen. The counter is controlled in a manner toprohibit it from counting beyond fifteen, so that motor hunting cannotadvance the counter after the fifteen steps are completed.

The complemented outputs from the four-bit binary counter are fed to thedigital-analog converter 204, and the converter generates adirect-current voltage which is proportional to the position of thepaperV during each step. This voltage is mixed with the signals fed tothe vertical deflection plate of the cathode-ray tube 18 to deflect theelectron beam in the direction of movement of the sensitized paper 26,and this lserves to compensate the beam position for such movement ofthe sensitized paper.

For example, at the beginning of the paper advance cycle, the counter isset to zero, so that the complemented outputs from the counter cause thedigital-analog converter 204 to produce a maximum output voltage. Thismaximum voltage causes the cathode-ray Ibeam of the tube 18 to beshifted in a vertical direction in the direction the paper is to bemoved and by an amount, equivalent, for example, to the space betweenone line and the next on the paper. Therefore, in carrying out thecompensation of the present invention, the cathode-ray tube 18 isimmediately caused to print the characters on the next line even beforethe paper is moved. As soon as the motor starts responding to the motorstep (MS) initiation pulse introduced to it, the counter 202 startscounting. As the counter accumlates its count, the amplitude of theanalog output from the converter 204 decreases, and the electron beam inthe cathode-ray tube 18 moves towards its normal position. This movementof the beam continues until the motor has actually moved through its 15and drawn the paper to the next line, at which time the motor stops andcompensation of the #beam ceases. This action causes the line of printto appear straight across the paper.

It will be appreciated, of course, that the stepper motor 104 iscontrolled, so as to step the paper from one line to the next as quicklyas possible, at which position it Waits until the next initiation pulsecauses it to repeat the operation for the `subsequent line. As notedabove, printing begins (with Ibeam compensation) while the stepper motoris moving the paper to the next line position, and just as soon as thestepper motor reaches the next line position, the compensation voltagevis removed, and the line scanning can proceed directly across the papersince it is now at rest. However, as long as the paper is in motion, thecompensation is generated, and effectively causes the electron beam toscan straight across the paper.

The circuit details for the photocell amplifier 200 are shown in FIGURE4. As illustrated, the output from the photocell 113 is .applied to aninput terminal 300 of the `amplifier which is coupled through a 300micromicrofarad capacitor 302 to the base of a PNP transistor 304. Thetransistor 304 may be of the type presently designated 2N3906. Theemitter of the transistor 304 is connected to the base of a similartransistor 306, the emitter of which is connected ot the positiveterminal of a 12 volt direct voltage source. The input terminal 300 isalso connected to the positive terminal through a `680 kilo-ohm resistor308, whereas the rbase of the transistor 304 is connected to thepositive terminal through a diode 310. The diode may be of the typepresently designated 2N3906.

The collector of the transistor 306 and the collector of the transistor304 are both connecteed to a grounded resistor 312 which may, forexample, have a value of 2.2 kilo-ohms. The collectors are alsoconnected through a l kilo-ohm resistor 314 to the base of an NPNtransistor 316. The emitter of the latter transistor is grounded, andthe collector is connected through a 1.2 kilo-ohm resistor 318 to thepositive terminal of a 4.5 volt direct voltage source. The collector ofthe transistor 316 is also coupled back to the base of the transistor304 through a 33 micromicrofarad capacitor 320. The collector is alsoconnected to an output terminal 322.

The low amplitude input signals introduced to the input terminal 300 areamplified in the solid state transistor amplifier of FIGURE and appearin amplified form at the output terminal 322. The amplified pulsesappearing at the output terminal 322 are applied to the four-bit counter202 which is shown in some detail in FIGURE 5. The motor step pulses(MS) are applied to an input terminal -400 of the counter in FIGURE 5 toreset the counter to zero. The input terminal 400 is connected to aninverter 402 which, in turn, is connected to the reset input terminals Cof a series of J--K fiip-fiops L1, L2, L4, L8 and L16. The ffip-fiopsL1, L2, L4, L8 and L16 are interconnected through a series of and gates404, 406 and 408, and corresponding inverters 410, 412 and 414, to forma usual binary counter. The complemented output terminals O of thevarious flip-flops are connected to corresponding output terminals 416,418, 420, 422 and 424 which represent, respectively, the binary valuesT72", E, L S and L.

The binary counter of FIGURE 5 is stepped from one counting condition tothe next by the successive pulses derived from the amplifier 200 ofFIGURE 4. Since the complemented output terminals of the counter areconnected to the digital-analog converter of FIG- URE 6, a maximumamplitude analog output from the converter is derived when the counteris reset to Zero (-l-.L-ITS') at the beginning of each step by the pulse(MS), and the analog output is reduced to zero as the counter counts upto fifteen.

When the counter reaches the count of fifteen, the terms L1, L2, L4 andL8 enable an and gate 426. This, in turn, disables an and gate 42S whichprevents the amplified pulses from the photocell amplifier 200 of FIGURE4 from stepping the counter any further. Only so long as the an gate 428is enabled are the amplified photocell pulses applied to the terminals(T) of the flip-flops through an inverter 430 to step the counter fromone count to the next. The next motor step pulse (MS) subsequentlyresets `the counter to zero, so that the process may be repeated.

As mentioned above, the output from the four-bit counter 202 of FIGURE 5is applied to the digital-analog converter 204 which is shown in somedetail in FIG- URE 6. The converter of FIGURE 6 is a simple resistiveladder which provides an analog output signal corresponding in amplitudeto the digital inputs derived from the counter. The digital inputs, asshown in FIG- URE 6, are applied to respective input terminals 500, 502,504, 506 and 508 of the converter which, in turn, are connected torespective amplifiers 510, 512, 514, 516 and 518. The outputs of theamplifiers are connected to the positive terminal of a 12 volt directvoltage source through respective 1.2 kilo-ohm resistors designated R1,R2, R3, R4 and R5. These outputs are also connected through respectivediodes C-Rl, CR2, CRS, CR4 and CRS to the positive terminal of a 7.5volt direct voltage source. These diodes may be of the type designated1N914.

The outputs from the amplifiers 510, 512, S14, 516, 518 are alsoconnected to a common lead 520 through precision resistors R9, R10, R11,R12 and R13. The resistor R9 has a resistance, for example, of 48kiloohms; the resistor R10 has a resistance of 24 kilo-ohms; theresistor R11 has a resistance of 12 kilo-ohms; the resistor R12 has aresistance of 6 kilo-ohms; and the resistor R13 has a resistance of 3.01kilo-ohms.

The common lead 520 is connected to the base of a grounded emitter PNPtransistor Q1 which may be of the type designated 2N3906 or 2N2907a. Thecollector of the transistor Q1 is connected through a 2.2 kiloohmresistor R20 to the negative terminal of the 12 volt direct voltagesource. The common lead 520 is also connected to that terminal through a22 kilo-ohm resistor R18. The collector of the transistor Q1 isconnected to the base of a PNP transistor Q3 which may be of the sametype. The collector of the transistor Q3 is directly connected to thenegative terminal of the 12 volt source; and its emitter is connectedthrough a 5 kilo-ohm potentiometer R21 and through a one kilo-ohmresistor R19 to the common lead 520. The potentiometer R21 serves as acompensation gain control. A capacitor C1 having a capacity, forexample, of micromicrofarads is shunted across the resistor R19 andpotentiometer R21. A diode CR9, which may be of the type designatedlNlOO, is shunted between the base and emitter of the transistor Q3.

The emitter of the transistor Q3 is connected through a 3.3 kilo-ohmresistor R27 to the base of a grounded emitter PNP transistor Q5. Thetransistor Q5 may be of the type designated 2N3904. Thecharacter-forming vertical deflection signals derived, for example, fromthe defiection signal forming generator 30 of FIGURE 1 are applied tothe base of the transistor Q5 by way, for example, of an input terminal511. The circuit of the transistor Q5, and the circuit of associatedtransistors Q6, Q11 and Q12 form the vertical deflection signalarnplifier 33 of FIGURE l.

The base of the transistor Q5 is also connected through a 3.3 kilo-ohmresistor R28 to a grounded capacitor C4, the capacitor having a value,for example, of .47 micromicrofarad. The junction of the resistor R28and capacitor C4 is connected to the movable contact of a potentiometerR26. The potentiometer R26 has a resistance of 5 kilo-ohms, and isconnected between the positive terminal of the 7.5 volt source and thenegative terminal of the l2 volt source. The potentiometer R26 serves asa vertical position control for the system.

The collector of the transistor Q5 is also connected to the base of anNPN transistor Q6 which, likewise, may be of the type designated 2N3904.The collector of the transistor Q6 is directly connected to the positiveterminal of a 24 volt direct voltage source. A resistor R31 having aresistance of 2.2 kilo-ohms is connected from that terminal to the baseof the transistor Q6. A capacitor C3 having a capacity of 33micromicrofarads is connected between the base and collector of thetransistor Q5. A diode CR11 of the type designated 1N100 is connectedbetween the base and the emitter ofthe transistor A vertical gainpotentiometer R33 having a resistance of kilo-ohms, and a 1.5 kilo-ohmresistor R34 are c011- nected between the base of the transistor Q5 andthe emitter of the transistor Q6.

The emitter of the transistor Q6 is connected through a 10 kilo-ohmresistor R37 to the base of a grounded emitter NPN transistor Q11 of thetype designated 2N3904. The base of the transistor Q11 is connected to aresistor IR39. The resistor R39 may have a resistance of 6.8 kilo-ohms,and it is connected to the negative terminal of the l2 volt source. Thecollector of the transistor Q11 is connected to the base of an NPNtransistor Q12 of the same type, and to a resistor R41. The resistor R41may have a resistance of 2.2 kilo-ohms, and is connected to the positiveterminal of the 24 volt direct voltage source. The collector of thetransistor Q12 is also connected to that terminal. The emitter of thetransistor Q12 is connected back to the base of the transistor Q11through a 10 kilo-ohm resistor R43. A diode CR14 of the type designatedINlOO is connected between the base and emitter of the transistor Q12.The emitter ofthe transistor Q12 is connected to the vertical deflectionplates of the cathode-ray tube 18 of FIGURE 1.

The invention provides, therefore, a high speed display system in whichany skew in the displayed characters is compensated and any tendency forthe instrument to overprint the information is obviated. This isachieved, as described herein, by means of a simple compensation circuitand system.

What is claimed is:

1. In an instrument for displaying and recording data and whichincludes: a cathode-ray tube having a viewing screen and further havingmeans for deflecting an electron beam across the viewing screan; meanshaving its output coupled to said beam-deflecting means and producingdcection signals for deflecting the electron beam in a predeterminedmanner to enable a sequence of characters t0 be displayed in a line onthe viewing screen; sensitized paper means positioned adjacent saidviewing screen for recording the line of characters displayed on saidviewing screen; and drive means including an electric stepping motor formoving said sensitized paper across said screen in a series of steps soas to enable the characters displayed in said line on said screen to berecorded in a series of successive lines on said paper; a linecompensation control system including: a converter circuit responsive toan applied digital input signal for producing an analog output signaland having its output coupled to said be'am deflecting means to causesaid electron beam to be deected in a direction transverse to theaforesaid line on the viewing screen thereof by an amount dependent onthe amplitude of the analog output signal produced by the convertercircuit; pulse generating means coupled to said stepping motor andproducing a predetermined number of electrical pulses for each step ofsaid motor; and control circuitry electrically coupled to said pulsegenerating means and responsive to the electrical pulse generatedthereby for introducing digital signals to said converter circuit tocause the amplitude of the analog signal generated by said convertercircuit to be a function of the displacement of said paper between oneline and the next.

2. The combination defined in claim 1, in which said pulse generatingmeans includes an optical disc mechanically coupled to said steppingmotor to be rotated thereby, a light source positioned on one side ofsaid disc, and a photo cell positioned on the other side of said disc.

3. The combination defined in claim 1, in -which said control circuitryincludes binary counter means electrically coupled to said pulsegenerating means for producing a binary coded output in response to thepulse produced by said pulse generating means, and in which said converter circuit includes a digital-analog converter for transforming saidbinary coded output from said binary counter means into an analogsignal.

4. The combination dened in claim 1, in which said analog signalproduced by said converter circuit has a maximum amplitude at thebeginning of each step of said stepper motor and is reduced in amplitudeduring such step.

References Cited UNITED STATES PATENTS 2,525,891 10/ 1950 Garman et al178--6.7 2,596,741 5/1952 Tyler et al. 346-110 X 2,736,770 2/ 1956McNaney 178-15 3,137,768 6/ 1964 Mullin 178-6.6 3,313,883 4/1967 Huntley178-15 JOSEPH W. HARTARY, Primary Examiner U.S. Cl. X.R. 178-6\.7, 15

